Comparison of polysomnography with ResCare Autoset in the diagnosis of the sleep apnoea/hypopnoea syndrome.

BACKGROUND Increasing referral numbers make the development of simplified accurate methods of diagnosing the sleep apnoea/hypopnoea syndrome highly desirable. The accuracy of one such system--the ResCare Autoset--has been examined. METHODS Thirty one consecutive patients assessed by polysomnography had simultaneous monitoring of their respiratory pattern using the Autoset system. The Autoset detects episodes of flattening of the flow/time profile using nasal cannulae. RESULTS There was a good correlation (r = 0.85) between the number of apnoeas+hypopnoeas/hour in bed recorded using polysomnography and the Autoset system. The median difference in such events was 3.1 (95% confidence interval 8.4 to -1.6)/hour in bed. In two patients the Autoset scored 70 apnoeas+hypopnoeas/hour in bed compared with 34 apnoeas+hypopnoeas with 35 arousals/hour in bed by polysomnography; however, this did not alter the diagnostic category of either patient. Autoset gave a sensitivity of 100%, specificity of 92%, positive predictive value of 92%, and negative predictive value of 100%, which was better than oximetry alone. A sleep study using the Autoset system costs 14 pounds compared with 126 pounds for polysomnography. CONCLUSIONS The Autoset is clinically useful for diagnosing the sleep apnoea/hypopnoea syndrome.